1. Technical Field
The present invention relates to a plasma reactor used for a semiconductor manufacturing process. More particularly, the present invention relates to a workpiece de-chucking device of a plasma reactor and a workpiece de-chucking method using the same.
2. Description of the Related Art
Commonly, ElectroStatic Chuck (ESC) is used to chuck a workpiece (e.g., a wafer or a glass substrate) to be etched or deposited with deposition materials, to the inside of a reaction chamber of a plasma reactor. The workpiece is chucked on the ESC by an attractive force of static electricity generated when a chucking power source is supplied to the ESC.
In order for an etching process or deposition process to be smoothly carried out, the workpiece has to be firmly chucked on the ESC. For example, the workpiece has to be chucked on the ESC enough to endure a pressure of 30 Torr or more of helium (He) gas that is a cooling gas applied to a rear surface of the workpiece. Accordingly, during the workpiece etching process or deposition process, a high-voltage Direct Current (DC) power source is supplied to an electrode of the ESC as a chucking power source.
In order to take out a workpiece completing etching or deposition treatment from the reaction chamber, a de-chucking process of de-chucking the workpiece firmly chucked to a top surface of the ESC from the ESC is needed. A conventional de-chucking method is briefly described below. If an etching process or deposition process ends, a chucking power source supplied to an ESC is cut off, and antistatic plasma is generated. By the antistatic plasma, charges existing between a workpiece and the ESC are completely discharged through a chamber body. If the antistatic plasma is off, the workpiece can be de-chucked from the ESC.
However, the conventional de-chucking method consumes a long time in completely discharging the charges between the workpiece and the ESC. Also, according to the conventional de-chucking method, it can frequently occur that the charges between the workpiece and the ESC remain without being completely discharged. This case can induce the popping phenomenon in which the workpiece is popped up without being well de-chucked from the ESC. Also, in a state where the workpiece is stuck to the ESC, the workpiece may be damaged due to a physical force resulting from the ascendance of a lifting unit. In case that the popping phenomenon takes place, the workpiece can leave its original position on the ESC, and particles can be generated.
If the workpiece leaves its original position on the ESC, this can become a cause of a failure of the workpiece because a position of the workpiece is changed when the workpiece is taken out from the reaction chamber and loaded in an external loading box or a next process for the workpiece is carried out. Also, in case that the popping phenomenon heavily occurs, the workpiece may be damaged.
Up to now, it is difficult to check if charges between a workpiece and an ESC are completely discharged. Thus, it is very difficult to reduce a popping or damage phenomenon occurring in a process of de-chucking the workpiece from the ESC, by the conventional de-chucking method.
On the other hand, during the etching process or deposition process and the de-chucking process, a surface of the ESC is contaminated due to polymer generated within the reaction chamber. Accordingly, after the workpiece is taken out from the reaction chamber, a dry-cleaning process of cleaning the surface of the ESC should be carried out for the sake of a next etching process or deposition process. In case that the etching process or deposition process is again carried out without the dry-cleaning process, the workpiece is not sufficiently firmly chucked to the ESC because of contaminants attached to the surface of the ESC. This causes an increase of a leakage of helium (He) gas applied to the rear surface of the workpiece, thus making a smooth workpiece treatment process difficulty. Accordingly, cleaning of the ESC is of much importance.
The conventional ESC cleaning process is separately carried out after a workpiece de-chucking process. Therefore, an ESC cleaning time is additionally consumed besides a workpiece de-chucking time. Resultantly, the number of processes (i.e., throughput) that can be treated by the plasma reactor during a set time is very limited. Thus, to increase the throughput of the plasma reactor, there is a demand for a method for reducing the workpiece de-chucking time and the ESC cleaning time.